Control circuits



April 12, 1949.

Filed June 1, 1946 FIG. I.

A.C. INPUT J. E. GANNON CONTROL CIRCUITS AIR RETURN l w W 2 Sheets-Sheet 1 TO ROOMS oqcr memos-m1 ROOM mamas-rmv Ll Ni. SWH'CH FIG. 2. M

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Ammm' April 12,1949. J. E. GANNON CONTROL CIRCUITS Filed June 1, 1946 2 Sheets-Sheet 2 FIGJL.

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(Jams ET e/v/va/v INVENTOR. BY 4 ATTORNEY Patented Apr. 12, 1949 CONTROL CIRCUITS James E. Gannon, Erie, Pa., assignor to American Electric Heating Company, Erie, Pa., a partnership Application June 1, 1946, Serial No. 673,743

3 Claims. 1.

My invention relates to control circuits, more particularly to control circuits for electrical heating systems, and the principal objectof my invention is to provide new and improved circuits of the character described.

Present day control circuits for electrical heating systems are either unreliable and noisy in op-- eration, or complicated and expensive in nature. In the former class may be grouped such controls which employ relays to operate the contactor switches used to connect or disconnect the resist ors with the current, source. In this group, and with a close setting of the, thermostat or other temperature responsive device, the noise of the contactors as they makeand break the circuit is of considerable annoyance. In the latter class may be grouped complicated circuits which control heat by phase shifting, such as is shown in the patent issued to E. D. Schneider, Number 2,250,207, or by capacitor discharge, as shown in the patent issued to H. L. Palmer, et al., Number 2,364,998.

My invention combines simplicity of control and construction with reliability and quietness of operation, and thus provides desirable features lacking in the prior art, especially that mentioned.

In addition, my invention provides means for eliminating so-called cold-seventy temperature in an area. heated, and alsov provides means, for relating the operation, of. the heating system with the outside. temperature. These, features, further combined with the features hereinbefore mentioned, provide control means for an electrical. heating system that possess all. the requirements necessary for modernclectric heating.

In the drawings accompanying this application, and forming a part of this specification, I have shown, for purposes of illustrationseveralembodiments which my invention may assume, and in these drawings:

Figure 1 is a generally schematic representation of an embodiment of my invention. as applied to, a conventional heating system,

Figure 2 is an electrical representation of the control circuit used in Figure 1:,

Figure 3 is an electrical representation of another embodiment of the invention, and

Figures 4 and 5 are graphic illustrations of the heat curve and energy cycles, respectively, of the embodiment shown in Figure 3.

Referring particularly to Figure 1, the invention may-be applied to a conventional heating system comprising duct Work l0, having an air return ll, and risers [2: leading. to various. rooms to'be' heated. Resistor means. t3; may be housed within the duct work it! in any suitable manner and at, any desired location. The resistor means may be composed of one or more heating elements, depending upon heating requirements.

As best shown in Figure 2, one side of the resistor means :3 is connected, by conductor i l, to one side of a source of current, a fused, line disconnect switch lii, preferably being interposed in both sides of the current source for protection purposes. The source, as is usual in most cases, is alternating current.

The other side of the current source is connected, by conductor iii, to an electric valve means which is so constructed and electrically connected to pass alternating current to the resistor means 13. It will be appreciated that the valve means herein employed provides switch means for controlling. flow of electric current to the resistor means 13.

Preferably, the valve means comprises electron tubes of the mercury vapor type, such as the ignitron type commercially available. In the particular embodiment shown, two ignitron tubes i1 and IS are used, each tube having an anode IELacathode 20 which is generally in the form of a mercury pool, and a starter or igniter 2| which dips into the mercury pool.

The tubes i'l--l8 are so connected as to oper ate like a single-pole magnetic contactor, but without the movement or noise inherent in operation of such contactors. The tubes, as shown, are connected in so-called back-to-back relation, so as to pass both halves of the alternating current. Thus, conductor it is connected, by conductor 22, to anode [9 of tube i l, and is also connected, by conductor 23, to cathode 20 of tube H3. The op posite side of resistor means I3 is connected, by conductor 24, to anode E9 of tube !8, and is also connected, by conductor 25, to cathode 2! of tube IT. This is the so-called back-to-back relation.

Since ignitron tubes have the characteristic of not being able to pass current until started by some means, the igniters 2i are included in the circuit, and as herein shown, igniters 2! are con nected together by a conductor 28. Cathode 20 of tube I7 is connected to conductor 2% and conductor 25 by branch conductor 2-1, and cathode 26 of tube lais connected to conductor 2i: and conductor 23 by branch conductor 28.

Keeping in mind that alternating current is of such characteristic that it flows alternately in opposite directions, for purposes of explanation of the operation, it will be assumed that the current first flows from conductor it through the resistor means l3 and to the conductor 5.4. To

do this, the current must also flow through one of the ignitron tubes. Since it is a generally ac cepted theory that current in an ignitron tube can only flow from anode to cathode, current, under the assumed conditions, can pass through tube H but not through tube l3. Therefore, cur-- rent under these conditions will flow from conductor 5, through conductor 22, through tube ll, conductor 25, resistor means |3, and to conductor l4. At the instant the current reverses, there is no current flow, but thereafter current will flow from conductor l4, through resistor means l3, conductor 24, through tube l8, conductor 23, to conductor 55. Of course, tubes ll, l8 will pass line current only if current is first forced into their igniters.

Current can be made to pass in either direction between the igniter and cathode, but the igniter will be damaged if current flows from the mercury-pool cathode into the igniter. Therefore, rectifiers 30, 3| are inserted in the lines including the igniter 2| of tube ll, and rectifiers 32, 33 are inserted in the lines including the igniter 2| of the tube 8 so that full current will be passed through the rectifiers in the direction of the arrows shown in Figure 2, and little or no current will be passed in the opposite direction. The rectifiers may be of the copper oxide type.

To control operation of the igniters 2|, and therefore operation of the tubes El, l8, switch means are included'in the circuit. As herein disclosed, switch means 35, 35 are included in series relation in the circuit, the switch 35 being actuated by a thermostat in the area to be heated, which thermostat may be termed the room thermostat. The switch 38 is actuated by a thermostat located adjacent the resistor means |3, which thermostat may be termed the duct thermostat. The duct thermostat prevents overheating of the resistor means l3 during the time the room thermostat is calling for heat, and also provides a means of regulating the heat of the resistor means 13 to regulate the temperature of the air delivered to the area to be heated.

In the commercially available ignitron tubes, as soon as line current flows through an ignitron tube, the arc drop across the tube decreases to about 15 to volts, and this small voltage cannot force current through the starter or igniter soon as the main line current flows through the respective ignitron tube. If the ignitron tube should fail to pass line current, the starter current would continue to flow and would overload the starter and rectifiers. Accordingly, a protective fuse 31 is inserted in the circuit to safeguard against this condition.

In operation, with both room and duct thermostats calling for heat, during one-half of the A. C. wave, current flows from conductor I6, through conductor 23, rectifier 32, conductor 26, closed switches 36, 35, fuse 31, rectifier and into igniter 2| of tube through anode 25 of tube ll, through conductor 25, resistor means l3, and to conductor It. This igniter current will make tube ll fire, passing the load current directly through conductors 25, 25, resistor means It, and to conductor 44.

During the opposite half of the A. C. wave, current flows iromconductor l4 through resistor means I3, conductor 25, rectifier 3| fuse 3i, closed switches 35, 35, rectifier 33, to igniter 2| of tube I8, through cathode 20 of tube l8, conductor 23, and to conductor Hi. This igniter current fires tube it, which passes load current directly through conductor 23 to conductor it.

Of course, it will be understood that circuit operation is under direct control of the room and duct thermostats, so that if either thermostat is not calling for heat, it will cause its switch to open the circuit.

teierring to Figure 3, a control circuit similar to the control circuit liereinbeiore described is used, and parts similar to those of Figure 2 will bear the same reference numeral but supplemented with the suihx a.

In this embodiment, the conductors Ma and lfia lead to a source of alternating current, the usual fused, disconnect switches |5a being in terposed in these lines. A heater unit ill is connected across the conductors I ia, lBa, by means of a conductor ill, a thermostatically controlled switch 42 being interposed in this conductor.

Also connected across the conductors Uta, lfia, as by means of conductors is, 44 are the motor portions 25, 46 of relays CR! and CR2, thermostatically controlled switches i'l, 48 being interposed in respective conductors 43, 44.

Beyond the ignitron tubes l'la, lBa, and under control thereof, are a blower motor 49, and resistor means comprising a series of units, here shown to be three in number and respectively designed 55, 5|, and 52, Contacts 53 of relay CR! also control heater unit 5|, and contacts 54 of relay CR2 also control heater unit 52.

The thermostats controlling switches 42, 41, and 48 are located outside of the area to be heated, and are preferably responsive to variations in temperatures outside of a building. For illustration purposes, the thermostat controlling switch 42 may be set to cut in the heating unit 4|! when the outside temperature drops below 70 F. Further, the thermostats controlling switches 41, 48 may be respectively set to actuat the relays CRl, CR2 to provide for energization of the heating units 5|, 52 when the outside tom-- perature drops, for example, below and 20 II, respectively. Of course, these units 5 l, 52 will not be energized until the respective outside temperatures are reached and the ignitron tubes lla,

Isa are passing line current.

In the embodiment shown in Figure 3, the heating unit 40 will be energized any time the outside temperature drops below, as an example, 70 F., regardless of whether or not the ignitron tubes are passing line current. When the outside temperature drops, as an example, below 40 F., the

I relay CRI is energized to close contacts 53 to permit heating unit 5| to be included in circuit when tubes Ha, |8a pass line current. And, when the outside temperature drops, as an example, below 20 F., the relay CR2 is energized to close contacts 54 to permit heating unit 52 to be included in circuit when tubes Ila, |8a pass line current. Heating unit 50, as in the case of resistor means I3, is only under control of tubes Ha, l8a.

It will be appreciated that each of the heating units may comprise one or more resistors, and these units may all be grouped in one locality, or may be positioned as desired. Preferably, all heating units are located in the duct work [0 to receive air moved by the blower 49.

Figures 4 and 5 respectively illustrate graphically the heat curve and the energy supplied, starting from a condition when the outside temperature is below 20 F. In this case, when the room thermostat and duct thermostat (controlling switches 35a and 36a) are calling for heat, all

of the heating elements 40, 50, 5|, and 52 will be energized.

When the duct temperature reaches a predetermined amount, as determined by the setting of the duct thermostat, all but the heating element 40 will be deenergized, and this is indicated by the numeral 55 in Figures 4 and 5. When the room temperature reaches the setting of the room thermostat, for example 70 F., the room thermostat will take over the control and will cause deenergization of all the heating elements, except the element 40. This is shown by numeral 55.

Latent heat will cause the temperature to rise slightly above 70 F., and the room will start cooling until it against drops to 70 F., when the room thermostat will again cause energization of the heating elements 50, 5|, and 52. However, since these elements are starting from cold condition, the room temperature will drop as Shown by ionmeral 57, until the heat of these elements again affects the temperature of the room.

By use of my invention, this drop below the setting of the room temperature will not be as pronounced as the customary drop shown in dotted lines 58, since the heating means as is constantly energized and a certain amount of heat is continuously available for the room. Further, when the blower motor :49 is actuated, heated air will be delivered to the room, despite the fact that the heating elements 50, 5|, and 52 are starting from a cold condition. In this manner, what is termed by the trade as cold-seventy is eliminated. It will be appreciated that the term cold-seventy would be modified, depending upon the setting of the room thermostat.

In the case where the outside temperature, as in the example herein disclosed, rises above F., the heating element 52 will not be cut in by the tubes Ila, [8a, since because of the relatively warmer outside temperature, less energy will be required. This condition is shown at 59 in Figure 5. Further, if the outside temperature, as in the example herein disclosed, rises above F., only the heating element will be cut in by the tubes IIa, [8a, and the energy supplied is illustrated by numeral 60 in Figure 5. Finally, if the outside temperature, as in the example herein disclosed rises above 70 F., the heating element at will be deenergized, and unless the room thermostat is set above 70 F., all heating elements will be out of operation, and the energy supply will drop to zero, as shown by numeral 6! in Figure 5.

From the foregoing, it will be apparent to those skilled in the art that I have accomplished at least the principal object of my invention, and it also will be apparent to those skilled in the art that the embodiments herein described may be variously changed and modified, without departing from the spirit of the invention, and that the invention is capable of uses and has advantages not herein specifically described; hence it will be appreciated that the herein disclosed embodiments are illustrative only, and that my invention is not limited thereto.

I claim:

1. A control circuit for an, electrical heating system for a building, adapted to control energy from an alternating current source, comprising: first heating element means; electric valve means, so constructed and electrically connected to pass alternating current to said first heating element 7 means, said first heating element means comprising units all under control of said electric valve means; interior thermostat means, for controlling operation of said valve means; first exterior thermostat means; switch means, actuated by said first exterior thermostat means, and connected in series with said valve means for controlling energization of at least certain of said units; second heating element means; second exterior thermostat means; and switch means, actuated by said second exterior thermostat means, for controlling energization of said second heating element means.

2. An electric heating system, comprising: heating element means connectable to a current source and comprising a plurality of sections; thermostatically controlled switch means afiected by the temperature without the area to be heated, and controlling current flow to certain of said sections; thermostatically controlled switch means, affected by the temperature of the area to be heated, for controlling current flow to all the remaining sections of said heating element means; and a plurality of thermostatically controlled switch means affected by the temperature without the area to be heated, said plurality of switch means being operable at different temperatures and each at a temperature lower than the setting of said first named thermostatically controlled switch means, and said second switch means controlling current fiow to only certain respective sections of said remaining sections.

3. An electric heating system, comprising: a first heating element; first thermostatically controlled switch means 'aifected by temperature comprising a plurality of sections; second thermostatically controlled switch means, affected by temperature within the area to be heated, for controlling current fiow to all sections of said second heating element; and third thermostatically controlled switch means, affected by temperature without the area to be heated, for controlling current flow to certain of the sections of said second heating element, said third switch means being set to energize said certain sections at a temperature lower than the setting of said first switch means.

JAMES E. GANNON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,044,269 Shaler Nov. 12, 1912 1,708,309 Knaak Apr. 9, 1929 2,058,252 Parsons Oct. 20, 1936 2,062,337 Stewart Dec. 1, 1936 2,080,799 Wiegand May 18, 1937 2,088,477 Knowles July 27, 1937 2,168,680 Nordgren Aug. 8, 1939 2,250,207 Schneider July 22, 1941 FOREIGN PATENTS Number Country Date 389,216 Great Britain Mar. 16, 1933 

